[Results]
The result of TLC
| Dye Mixture (in MeOH) | Rf (eluent in EtOAc) | Rf (eluent in EtOAc : MeOH = 1 : 1) |
| Sudan IV | 0.964 | 0.965 |
| Bismark Brown | 0.821 | 0.929 |
| Rhodamine B | 0.071 | 0.429 |
| Fast Green | 0.036 | 0.893 |
[Discussion]
The structures of chemical compounds we used as dye mixture are as follows ;
* In TLC experiment, we had traveled through EtOAc for developing eluent first. Then we changed eluent as EtOAc : MeOH in proportion of 1:1. Comparing Rf values of these two results, we found that every spot with 1:1 proportion of EtOAc : MeOH eluent was displaced more far away when developed with EtOAc eluent. In other words, Rf value was increased at every spot. Through this experiment, we knew migration distance was changed by eluent, even developing same substances. Relatively higher Rf value in TLC means relatively more nonpolar. It is because TLC surface is polar, and development eluent becomes more polar because of MeOH's polarity. Therefore, migration distance is increased because the compound's affinity to mobile phase increased.
* Polarity difference between stationary phase and mobile phase decreased in case of 1:1 proportion of EtOAc : MeOH eluent. However, their sequence of migration distance was not changed. (We made mistake on result paper. We confused of the data of each sample.) Polarity sequence of these sample is Rhodamine B > Fast Green > Bismark Brown > Sudan IV, according to our experiment. This sequence is caused by each compound's functional group. Rhodamine B has N+ in its structure, so it is very polar. Bismark Brown has several amino groups which make hydrogen bond between silica gel of TLC surface. Sudan IV has relatively nonpolar structure. Fast Green also has -OH functional group but it has several benzene which is hydrophobic.
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